The call from the White House was not unexpected. Back in New Jersey for the August recess, Sen. Robert Menendez answered the phone Thursday evening, fully expecting to learn final details of President Obama's plan for attacking Syria.

The Democratic senator, a social liberal with foreign policy views that border on the hawkish, is in his rookie season as chairman of the Foreign Relations Committee. The Syria chemical-weapons crisis would mark Menendez's first moment front-and-center on the international stage as leader of the critical Senate panel.

It was to be a chance for the backroom brawler from the city streets of North Jersey to finally step out of the shadow of his predecessors, John Kerry (now secretary of state) and Joe Biden (now vice president) -- and to prove to his critics he deserved his coveted spot.

That Thursday phone call was not unexpected. But it did offer a surprise. A huge surprise. Instead of hearing strike details, Menendez listened as the president explained he was thinking of altering course and holding off on an attack so he could secure congressional approval for military action.

Never a fan of Obama or his laid-back style, which the administration described during the build-up to effort to depose Libyan strongman Moammar Gadhafi as "leading from behind," Menendez was now on the verge of becoming the unlikely go-to guy for a White House quickly bleeding support and credibility.

Less than two days later, Obama went to the Rose Garden to make official his plan to go to Capitol Hill. With that, the president put Menendez -- a man he doesn't like -- in charge of what could be the most critical foreign-policy initiative of his fledgling second term.

"When you're president, you don't always get to choose the legislator you need on a particular issue," said Princeton University public affairs professor Julian Zelizer, an expert on presidential leadership.

But, Zelizer acknowledged, Obama's decision to deputize Menendez on such a critical issue is "risky."

"The whole thing (Syria attack question) is risky at this point and, on top of it, to have a Democratic who's shaky on you can make you nervous," Zelizer said. "Obama is going to be a little bit nervous. This is someone he doesn't fully trust."

The curtain will rise on this new Menendez-Obama alliance when the senator gavels his committee to order this afternoon. Among the first witnesses expected to be called are Kerry, Defense Secretary Chuck Hagel and Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff.